5. Conclusions

Enterobacter aerogenes, Escherichia coli, Staphylococcus aureus) and susceptible collection strains (Staphylococcus aureus ATCC 6538, Salmonella choleraesuis ATCC 10708; Pseudomonas aeruginosa ATCC 15442), the authors indicated that clove (Caryophyllus aromaticus) and jambolan (Syzygium jambolanum) were the strongest inhibitors (64.2 and 57.1%) of the used bacterial strains. Furthermore, their activity was the most remarkable (83.3%) against the germs resistant to antibiotics, where their synergistic activity with the antibiotics was also observed. Interestingly, plants such as sage and yarrow, well known for their antiseptic properties, showed no effect on the tested MDR bacteria. Some of the plants showed in specific cases a homeopathic-like effect, i.e., clove, jambolan, pomegranate, and thyme extracts, when used in lower concentrations but combined

with ineffective antibiotics against Pseudomonas aeruginosa [26, 27, 29, 83, 84].

efficacy against

E. coli O157:H7 S. enteritidis

Salmonella essen, Salmonella enteritidis, ETEC, Salmonella choleraesuis, Salmonella typhimurium

aureus, E. coli Salmonella Enteritidis

Staphylococcus aureus, E. coli

MDR E. coli Retail

Strain origin

chicken meat samples

Reference laboratory

Poultry swine

Bovine Disc

Bovine Disc

S. aureus Bovine Disc

Evaluation method(s)

Broth microdilution

Broth microdilution

Broth microdilution

diffusion broth microdilution

diffusion broth microdilution

diffusion broth microdilution Mechanism(s) of action

Inhibition of the biofilm formation for S. enteritidis

Not determined

Not determined

Not determined

Not determined

Not determined References

[87]

[16]

[88]

[89, 90]

[91]

[92]

Name Extract type In vitro

Ethanolic extracts

extracts

Ethanolic extracts

Hydroalcoholic extracts

Essential oils E. coli,

Essential oils Staphylococcus

Table 1. Herbal extracts demonstrated to inhibit MDR zoonotic strains of animal origin.

Syzygium aromaticum and Cinnamomum > Mentha spicata L. and Coriandrum sativum L. > Allium sativum L. and

102 Antimicrobial Resistance - A Global Threat

Olea europaea Ethanolic

Nigella sativa L.

Origanum

vulgare > Thymus zygis Thymus mastichina

Melissa officinalis > Thymus vulgaris and Salvia officinalis

Allium sativum L., Elwendia persica (Bunium persicum), Oryza sativa L. and Triticum aestivum L.

Achyranthes aspera L., Ficus carica, Malva parviflora, Vernonia species, Solanum hastifolium, Calpurnia aurea Benth, Nicotiana tabacum L., Ziziphus spina-christi, Croton macrostachyus

In spite of extensive research carried out on healing effects of plants, antibacterial effects included, the subject is far from being closed, the high variety of plant species providing a strong support for investigation. Although numerous researchers deal with the effects of individual compound against bacteria, those extracts containing multiple active substances and exerting simultaneously antibacterial and immune-enhancing effects are favored. Veterinary and zoonotic pathology, due to the presence of MDR bacteria, could equally benefit of the discovery of plant extracts with high antibacterial potential, useable separately or in combination with otherwise inefficient classical antibacterial therapies.
